BIOSORPTION OF NICKEL FROM AQUEOUS SOLUTION BY FENTON ACTIVATED AND SODIUM HYDROXIDE TREATED LEUCAENA LEUCOCEPHALA PODS

Abstract

Leucaena leucocephala biomass was modified using sodium hydroxide and Fenton’s reagent and their effectiveness for the removal of metal from aqueous solution was investigated under various experimental conditions such as pH, contact time, concentration, biomass dose, adsorption capacity, recovery and temperature. Adsorption data were interpreted in terms of Langmuir, Freundlich and Temkin models. The data obtained provide strong support for the adsorption of Ni (II) ion onto the three adsorbents. The high correlation co-efficient( R2) values obtained using the three adsorbents showed that the data were able to fit sufficiently into Langmuir, Freundlich and Temkin isotherms. The adsorption data were also verified using Pseudo-first order and Pseudosecond order kinetic models and high correlation co-efficient values were obtained for Pseudo second order kinetic model which proved that the data obeyed Pseudo-second order kinetic model. Results obtained showed that optimum adsorption took place at pH 6 and at the optimum time of 240 minutes for fenton activated Leucaena leucocephala, untreated Leucaena leucocephala and NaOH treated Leucaena leucocephala having 85.51, 76.60 and 92.44 % respectively. Sorption capacity was conducted at ten cycles for the three adsorbents, there was a gradual decrease in the adsorbent capacity till 10th cycle. Recovery of the adsorbed metal was carried out using different concentrations of HCl (0.01, 0.02, 0.03, 0.04 and 0.05) and best recovery for the three adsorbents occurred at 0.03M HCl. Effect of temperature were investigated at 35, 45, 55, 65, and 750 C.It was discovered that increase in temperature did not favour the adsorption process, but percentage metal bound reduced with increase in temperature. The thermodynamic parameters investigated showed that ΔH was negative indicating that heat was given out in the process. It also showed that ΔG was negative at 298 and 308K indicating a spontaneous reaction, while ΔS was positive indicating certain degree of randomness. The results show that NaOH treated Leucaena leucocephala have highest uptake of Ni2+ ion from solution followed by fenton activated Leucaena leucocephala and unmodified Leucaena leucocephala